U.S. patent number 5,654,621 [Application Number 08/424,371] was granted by the patent office on 1997-08-05 for method and arrangement for automatic contactless charging.
This patent grant is currently assigned to Daimler-Benz Aktiengesellschaft. Invention is credited to Anton Seelig.
United States Patent |
5,654,621 |
Seelig |
August 5, 1997 |
Method and arrangement for automatic contactless charging
Abstract
In a process for contactless energy transmission in charging the
battery of a vehicle, in particular an electric car, by means of an
inductive transmitter having a primary element (1) and a secondary
element (2) which is attached to the vehicle, the secondary element
(2) is made freely accessible and the primary element is power
driven to move in all three spatial coordinates within a
predetermined spatial area. In this process the primary element (1)
and the secondary element (2) are placed, under sensor control, in
predetermined positions relative to each other and then electrical
energy is transmitted in the medium frequency range by means of the
inductive transmitter.
Inventors: |
Seelig; Anton (Floersheim,
DE) |
Assignee: |
Daimler-Benz Aktiengesellschaft
(Stuttgart, DE)
|
Family
ID: |
6471488 |
Appl.
No.: |
08/424,371 |
Filed: |
August 16, 1995 |
PCT
Filed: |
October 27, 1993 |
PCT No.: |
PCT/EP93/02976 |
371
Date: |
August 16, 1995 |
102(e)
Date: |
August 16, 1995 |
PCT
Pub. No.: |
WO94/10004 |
PCT
Pub. Date: |
May 11, 1994 |
Foreign Application Priority Data
|
|
|
|
|
Oct 28, 1992 [DE] |
|
|
42 36 286.5 |
|
Current U.S.
Class: |
320/108;
320/109 |
Current CPC
Class: |
H02J
7/025 (20130101); B60L 53/11 (20190201); B60L
53/38 (20190201); B60L 53/126 (20190201); H02J
50/12 (20160201); H01F 38/14 (20130101); B60R
16/03 (20130101); H02J 2310/46 (20200101); Y02T
90/12 (20130101); Y02T 90/128 (20130101); Y02T
10/7005 (20130101); Y02T 90/121 (20130101); Y02T
10/7072 (20130101); Y02T 90/122 (20130101); Y02T
10/70 (20130101); Y02T 90/14 (20130101); Y02T
90/125 (20130101) |
Current International
Class: |
H02J
7/02 (20060101); H01F 38/14 (20060101); B60R
16/02 (20060101); H01M 010/44 () |
Field of
Search: |
;320/2,21,28,54 ;901/17
;364/483,550 ;336/DIG.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Hands Free Electric Vehicle Charging", Jun., 1992, No. 338,
Emsworth, Great Britain, p. 517..
|
Primary Examiner: Wong; Peter S.
Assistant Examiner: Toatley, Jr.; Gregory J.
Attorney, Agent or Firm: Spencer & Frank
Claims
I claim:
1. A method of contactless energy transmission during charging of a
battery of a vehicle using an inductive transmission arrangement
which includes:
a primary inductive element and a secondary inductive element, the
secondary inductive element being disposed on the vehicle, the
primary inductive element being movable with respect to the
vehicle, the primary inductive element for moving into an approach
position with respect to the secondary inductive element to achieve
magnetic coupling with the secondary inductive element, and
a charging device having an inverter for supplying the primary
inductive element with a current having a frequency greater than
about 20 kHz, the charging device additionally having a
demodulation apparatus, and coupling detection circuitry which
includes a peak rectifier, an analog-digital converter, a memory
controlled by a clock generator, and a comparison stage,
wherein capacitors are provided which resonate with the inductance
of the primary inductive element and the inductance of the
secondary inductive element, there being an a gap on the order of
centimeters between the primary and secondary inductive
elements,
wherein a battery state detection and charging current control
means is provided in the vehicle,
wherein a means of contactless transmission of information from the
vehicle to the charging device is provided in the vehicle, the
means for contactless transmission of information including a high
frequency generator disposed in the vehicle for producing a high
frequency signal, and a modulating apparatus configured as a
frequency modulator for producing a modulated high frequency
signal,
wherein an orientation signal emitter is provided on the vehicle to
supply an orientation signal,
wherein there is a charging current setter associated with the
inverter of the charging device, and
wherein there is at least one electronic switch associated with the
inventer, the method comprising:
(a) measuring a battery charging current and determining a
deviation of the measured battery charging current from a
predetermined desired charging current value, with the battery
state detection and charging current control means;
(b) transmitting the determined charging current deviation, under
control of the means for contactless transmission of information,
to the charging current setter associated with the inverter of the
charging device, step (b) including
(b-1) modulating the high frequency signal with a charging current
deviation signal produced by the battery state detection and
charging control means, using the modulating apparatus,
(b-2) transmitting the modulated high frequency signal produced in
step (b-1) through an electromagnetic field to the demodulation
apparatus of the charging device,
(b-3) using the demodulation apparatus to regenerate the charging
current deviation signal, and
(b-4) supplying the regenerated charging current deviation signal
to the inverter;
(c) controlling switching time or switching frequency of the at
least one electronic switch of the inverter supplying the current
to the primary inductive element, so that the charging current
deviation becomes zero; and
(d) before steps (a) through (c) are conducted, finding a favorable
approach position and magnetic coupling between the movable primary
inductive element and the secondary inductive element disposed on
the vehicle, step (d) including
(d-1) supplying an orientation signal from the orientation signal
emitter provided on the vehicle to the modulation apparatus,
(d-2) modulating the high frequency signal with the orientation
signal as the primary inductive element approaches the secondary
inductive element, and
(d-3) transmitting the modulated signal produced in step (d-2) from
the vehicle to the charging device,
(d-4) demodulating the signal transmitted in step (d-3), and
(d-4) using the coupling detection circuitry to indicate whether an
amplitude of the orientation signal, and, therefore, coupling
between the primary inductive element and the secondary inductive
element disposed on the vehicle, increases, decreases, or remains
the same.
2. A method as defined in claim 1, wherein, the movable primary
inductive element is attached to a moveable arm and moved by drive
motors in three spatial coordinates to approach the secondary
inductive element,
wherein the secondary inductive element is positioned, with the
vehicle, in a spatial region reachable by the primary inductive
element attached to the moveable arm,
wherein, as a function of output signals of the comparison stage,
the drive motors which move the movable arm are set in operation
and halted by drive guide and coupling means, the drive guide and
coupling means implementing conventional drive control and
regulating functions,
wherein the demodulator identifies the orientation signal emitted
from the vehicle and supplies it to the drive guide and coupling
means, and
wherein the drive guide and coupling means halts all of the drive
motors and emits a signal indicating coupling has been achieved
when an evaluation of the output signals of the comparison stage
indicates no increase in the amplitude of the received orientation
signal.
3. A method as defined in claim 2, wherein the signal indicating
coupling has been achieved causes a keyed signal emitter to switch
the inverter on and off in a rhythmical fashion,
wherein the signal indicating coupling has been achieved is
transmitted to the vehicle and regenerated by a keyed signal
demodulator, switches off the orientation signal, and switches on a
charging initiation signal for a predetermined pulse time
duration,
wherein the charging initiation signal is switched off by the
modulation apparatus after termination of the predetermined pulse
time duration, and the charging current deviation signal is
connected to the modulation apparatus, and
wherein the charging initiation signal demodulated and received by
the charging device connects a current guide input of the inverter
to the charging current deviation signal subsequently emitted by
the demodulator.
4. A method as defined in claim 2, further comprising:
automatically returning the primary inductive element to a resting
position after a charging process has ended,
wherein a charging end signal transmitted by the vehicle resets a
charging operation memory for switching off the inverter by means
of a current reference variable changeover switch for switching a
current reference value input from the modulator to the current
reference variable switched on prior to the charging process,
wherein the charging end signal is also supplied to the drive guide
and coupling means, and triggers a backward movement of the drive
motors,
wherein end switches halt the drive motors in a resting position of
the movable arm with the primary inductive element, and cause the
drive guide and coupling means to emit a start release signal,
wherein the start release signal is supplied to a keyed signal
generator means for switching the inverter on and off in a
rhythmical manner,
wherein the start release signal is received at the vehicle and
regenerated by a keyed signal demodulator, resets a charging end
signal generator, and brings a start signal generator into a
vehicle ready to start state.
5. A method of contactless energy transmission during charging of a
battery of a vehicle using an inductive transmission arrangement
which includes:
a primary inductive element and a secondary inductive element, the
secondary inductive element being disposed on the vehicle, the
primary inductive element being movable with respect to the
vehicle, the primary inductive element for moving into an approach
position with respect to the secondary inductive element to achieve
magnetic coupling with the secondary inductive element, and
a charging device having an inverter for supplying the primary
inductive element with a current having a frequency greater than
about 20 kHz,
wherein capacitors are provided which resonate with the inductance
of the primary inductive element and the inductance of the
secondary inductive element, there being a gap on the order of
centimeters between the primary and secondary inductive
elements,
wherein a battery state detection and charging current control
means is provided in the vehicle,
wherein a means for contactless transmission of information is
provided on the vehicle, the means for contactless transmission of
information including a high frequency generator, a modulating
apparatus, and a charging current deviation indicator,
wherein there is a charging current setter associated with the
inverter of the charging device, and
wherein there is at least one electronic switch associated with the
inventer,
the method comprising:
(a) measuring a battery charging current and determining a
deviation of the measured battery charging current from a
predetermined desired charging current value, with the battery
state detection and charging current control means, the battery
state detection and charging current control means including a
battery state detection means a charging current controller, and a
measurement controller; step (a) including
(a-1) transmitting a desired value for a charging current from the
battery state detection means to the charging current
controller,
(a-2) obtaining a measuring signal with the aid of the measurement
converter, the measuring signal being proportional to the current
induced in the secondary inductive element, and
(a-3) supplying the measuring signal to the charging current
controller, the charging current controller forming a charging
current deviation signal from the desired value for a charging
current and the measuring signal;
(b) transmitting the determined charging current deviation, under
control of the means for contactless transmission of information,
to the charging current setter associated with the inverter of the
charging device, step (b) including
(b-1) supplying the charging current deviation signal to the
charging current deviation indicator, and
(b-2) using the charge current deviation indicator to connect the
charging current deviation signal to the modulating apparatus,
which in turn modulates a high frequency signal generated by the
high frequency generator;
(c) controlling switching time or switching frequency of the at
least one electronic switch of the inverter supplying the current
to the primary inductive element, so that the charging current
deviation becomes zero; and
(d) when the battery is charged, emitting a signal from the battery
state detection means to indicate the battery is charged, the
signal emitted by the battery state detection means switching the
charging current deviation signal off at the modulating apparatus
by resetting the charging current deviation indicator, and
producing a charging end signal for transmission to the charging
device and to the modulating apparatus to turn off the modulating
apparatus.
6. A method as defined in claim 5, wherein the means for
contactless transmission of information from the vehicle to the
charging device includes a high frequency generator disposed on the
vehicle for producing a high frequency signal, and a modulation
apparatus configured as a frequency modulator for modulating the
charging current deviation, thereby producing a modulated high
frequency signal,
wherein the modulated high frequency signal is transmitted through
an electromagnetic field to a demodulation apparatus at the
charging device,
wherein the demodulation apparatus regenerates the signal for the
charging current deviation in the charging device, and
wherein the regenerated signal is supplied to the inverter that
produces the high frequency current.
7. An apparatus for contactless energy transmission,
comprising:
a primary inductive element and a secondary inductive element, the
secondary inductive element being disposed on a vehicle, the
primary inductive element being movable with respect to the vehicle
to a position at which the primary inductive element is spaced
apart from the secondary inductive element to form a transformer
with a gap,
a charging device having a capacitor which is connected in series
with the primary inductive element and having an inverter for
supplying the primary inductive element with an oscillating current
via the capacitor, the inverter having an inverter frequency
greater than about 20 kHz,
another capacitor carried by the vehicle, the another capacitor
being connected in parallel to the secondary inductive element, the
capacitors having capacitances which are selected so that the
capacitors resonate with the transformer with a gap at around the
inverter frequency; and
means for adjusting the amplitude of oscillation of the oscillating
current by changing the inverter frequency,
wherein the diameter or outer dimensions of the primary inductive
element and the secondary inductive element are approximately ten
to twenty times the gap width which remains between the two
transmission elements when they form the transformer with a
gap.
8. An apparatus as defined in claim 7, further comprising means for
detecting a charging current deviation, wherein the secondary
inductive element disposed on the vehicle serves as a transmission
element for contactless transmission of a high frequency signal for
transmitting the charging current deviation from the vehicle to the
charging device.
9. An apparatus as defined in claim 8, wherein the primary
inductive element serves as a transmission element of the charging
apparatus which receives the high-frequency signal containing the
charging current deviation.
10. An apparatus as defined in claim 7, wherein the primary
inductive element and the secondary inductive element have a shell
or disk shape, and wherein a winding height is small relative to
the diameter or outer dimensions of the elements.
11. An apparatus as defined in claim 7, wherein the gap between the
primary and secondary inductive elements, when they form the
transformer with a gap, lies in a plane, and wherein the primary
inductive element is positioned on one side of this plane and the
secondary inductive element is positioned on the other side.
12. A method according to claim 11, wherein the step of adjusting
the amplitude of the oscillating current comprises:
measuring a battery charging current and determining a deviation of
the measured battery charging current from a predetermined desired
charging current value, with a battery state detection and charging
current control means provided in the vehicle;
transmitting the determined charging current deviation, under
control of a means for contactless transmission of information
provided in the vehicle, to a charging current setter associated
with the inverter of the charging device; and
controlling a switching frequency of at least one electronic switch
provided in the inverter so that the charging current deviation
becomes zero.
13. A method as defined in claim 12, wherein the means for
contactless transmission of information from the vehicle to the
charging device includes a high frequency generator disposed on the
vehicle for producing a high frequency signal, and a modulation
apparatus configured as a frequency modulator for producing a
modulated high frequency signal,
wherein the modulated high frequency signal is transmitted through
an electromagnetic field to a demodulation apparatus at the
charging device,
wherein the demodulation apparatus regenerates the signal for the
charging current deviation in the charging device, and
wherein the regenerated signal is supplied to the inverter.
14. A method as defined in claim 12, wherein a battery state
detection means is disposed on the vehicle and transmits a desired
value for a charging current to a charging current controller,
wherein a measuring signal, obtained with the aid of a measurement
converter and proportional to the current transmitted to the
primary inductive element, is additionally supplied to the charging
current controller,
wherein the charging current controller forms a charging current
deviation signal from the desired value for a charging current and
the measuring signal, and supplies the charging current deviation
signal to a charging current deviation indicator which connects the
charging current deviation signal to the modulating apparatus,
which in turn modulates the high frequency generator, and
wherein, when the battery is charged, the battery state detection
means emits a signal indicating the battery is charged which
switches the charging current deviation signal off at the
modulating apparatus by resetting the charging current deviation
indicator, and produces a charging end signal for transmission to
the charging device and to the modulating apparatus to turn off the
modulating apparatus.
15. A method as defined in claim 13, wherein the step of moving the
primary inductive element comprises:
emitting an orientation signal from an orientation signal emitter
provided on the vehicle, and supplying the orientation signal to
the modulation apparatus to produce an orientation-modulated high
frequency signal as the primary inductive element approaches the
secondary inductive element, and transmitting the
orientation-modulated high frequency signal from the vehicle to the
charging device,
wherein the charging device further includes coupling detection
circuitry, including:
a peak rectifier,
an analog-digital converter,
a memory controlled by a clock generator, and
a comparison stage, and
wherein signals from the coupling detection circuitry indicate
whether an amplitude of the orientation signal, and, therefore,
coupling between the primary inductive element and the secondary
inductive element disposed on the vehicle, increases, decreases, or
remains the same.
16. A method as defined in claim 15, wherein the movable primary
inductive element is attached to a moveable arm and moved by drive
motors in three spatial coordinates to approach the secondary
inductive element,
wherein the secondary inductive element is positioned, with the
vehicle, in a spatial region reachable by the primary inductive
element attached to the moveable arm,
wherein, as a function of output signals of the comparison stage,
the drive motors which move the movable arm are set in operation
and halted by drive guide and coupling means, the drive guide and
coupling means implementing conventional drive control and
regulating functions,
wherein the demodulator identifies the orientation signal emitted
from the vehicle and supplies it to the drive guide and coupling
means, and
wherein the drive guide and coupling means halts all of the drive
motors and emits a signal indicating coupling has been achieved
when an evaluation of the output signals of the comparison stage
indicates no increase in the amplitude of the received orientation
signal.
17. A method as defined in claim 16, wherein the signal indicating
coupling has been achieved causes a keyed signal emitter to switch
the inverter on and off in a rhythmical fashion,
wherein the signal indicating coupling has been achieved is
transmitted to the vehicle and regenerated by a keyed signal
demodulator, switches off the orientation signal, and switches on a
charging initiation signal for a predetermined pulse time
duration,
wherein the charging initiation signal is switched off by the
modulation apparatus after termination of the predetermined pulse
time duration, and the charging current deviation signal is
connected to the modulation apparatus, and
wherein the charging initiation signal demodulated and received by
the charging device connects a current guide input of the inverter
to the charging current deviation signal subsequently emitted by
the demodulator.
18. A method as defined in claim 16, further comprising:
automatically returning the primary inductive element to a resting
position after a charging process has ended,
wherein a charging end signal transmitted by the vehicle resets a
charging operation memory for switching off the inverter by means
of a current reference variable changeover switch for switching a
current reference value input from the modulator to the current
reference variable switched on prior to the charging process,
wherein the charging end signal is also supplied to the drive guide
and coupling means, and triggers a backward movement of the drive
motors,
wherein end switches halt the drive motors in a resting position of
the movable arm with the primary inductive element, and cause the
drive guide and coupling means to emit a start release signal,
wherein the start release signal is supplied to a keyed signal
generator means for switching the inverter on and off in a
rhythmical manner, and
wherein the start release signal is received at the vehicle and
regenerated by a keyed signal demodulator, resets a charging end
signal generator, and brings a start signal generator into a
vehicle ready to start state.
19. A method of contactless energy transmission during charging of
a battery of a vehicle using an inductive transmission arrangement,
the inductive transmission arrangement including
a primary and a secondary inductive element, the secondary
inductive element being disposed on the vehicle, the primary
inductive element being movable with respect to the vehicle to a
position adjacent the secondary inductive element to achieve
magnetic coupling with the secondary inductive element,
plastic material on the primary and secondary inductive elements
for electrical insulation and protection, the plastic material on
each of the inductive elements having a respective thickness,
a charging device having a capacitor which is connected in series
with the primary inductive element and having an inverter for
supplying an oscillating current to the primary inductive element
via the capacitor, the inverter having an inverter frequency which
is greater than about 20 kHz, and
another capacitor carried by the vehicle, the another capacitor
being connected in parallel to the secondary inductive element,
wherein said method comprises the steps of:
moving the primary inductive element toward the secondary inductive
element to a position at which the primary inductive element is
spaced apart from the secondary inductive element to form a
transformer with a gap, the gap between the primary and secondary
inductive elements being at least as large as the sum of the
thickness of the plastic material on the primary inductive element
and the thickness of the plastic material on the secondary
inductive element, the capacitors having capacitances which are
selected so that the capacitors resonate with the transformer with
a gap at around the inverter frequency; and
adjusting the amplitude of oscillation of the oscillating current
by changing the inverter frequency.
20. A method as defined in claim 19, wherein the diameter or outer
dimensions of the primary inductive element and the secondary
inductive element are approximately ten to twenty times the gap
width which remains between the two transmission elements when they
form the transformer with a gap, this gap width being up to the
order of centimeters.
21. A method as defined in claim 20, further comprising means for
detecting a charging current deviation with a detecting means in
the vehicle, and using a modulated high frequency signal for
transmitting the charging current deviation from the vehicle via
the secondary inductive element to the charging device.
22. A method as defined in claim 21, wherein the primary inductive
element receives the modulated high-frequency signal containing the
charging current deviation.
23. A method as defined in claim 20, wherein the primary inductive
element and the secondary inductive element have a shell or disk
shape, and wherein a winding height is small relative to the
diameter or outer dimensions of the elements.
24. A method as defined in claim 19, wherein the step of moving the
primary inductive element is conducted by moving the primary
inductive element along three spatial coordinates.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and an arrangement for
contactless energy transmission during charging of a vehicle
battery, e.g., of an electric car.
2. Background Information
It is already known to charge the battery of electric vehicles by
means of inductive charging stations (Rhein-Main-Presse, Jul. 18,
1992). To this end, a charging coil is manually inserted into the
slot of an adapter disposed on the outside of the vehicle, and
electrical energy is subsequently transmitted from the charging
device to the battery. Although this system of energy transmission
operates reliably and is safe to use, since the secondary coil is
protected in the adapter, the insertion of the charging coil into
the adapter is oriented toward conventional fueling of a
gasoline-powered car and is rather awkward in terms of handling.
Moreover, the consequences of having the adapter disposed on the
outside of the electric car can include mechanical, aerodynamic and
aesthetic disadvantages to the vehicle. Another disadvantage is a
path-impairing cable is connected to the electric car, and is in
place for a significantly longer time during charging of the
battery than, for example, the connection of a gasoline hose to a
gasoline vehicle. Furthermore, charging devices that have different
charge outputs and are produced by different manufacturers should
be able to be coupled to the vehicle without great effort. Slow
charging with a home charging device that has a low output and fast
charging using a high-output charging device, for example in a
parking garage while the owner shops, will become standard
practice. Because the dimensions of the charging coil vary with the
output, in an arrangement that includes a coil to be pushed into a
slot, both the slot and the coil must be of the dimensions of the
highest output.
Therefore, the problem exists of achieving simple and convenient
handling in addition to high operating and application reliability
during charging of the battery of an electric car. It is to be
noted here that, on the one hand, simple and convenient handling of
such a system, without an excessively high mechanical outlay,
requires easy accessibility to the inductive energy-transmission
components, but, on the other hand, the greater danger of
impairment of the operating reliability and safety in use exists
because of the stronger association with environmental influences,
particularly pollution or the like.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of
contactless energy transmission during charging of an electric
vehicle, the method being simple and convenient for the user with
high operating reliability and safety in use. A further object of
the invention is to provide a corresponding apparatus which also
permits the coupling of inductive energy-transmission components
designed for different outputs without an extra expenditure for the
charging device of lesser output. This object is accomplished by
the features the advantageous embodiments of the invention which
are disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in detail below in conjunction with
drawing figures, in which:
FIG. 1 schematically shows an apparatus according to the invention,
and illustrates the method according to the invention for
contactless energy transmission;
FIG. 2 schematically shows an embodiment of an inductive
transmitter;
FIG. 3 shows a preferred embodiment of the electronic components of
the apparatus of the invention minus the sensor arrangement;
FIG. 4 shows an equivalent circuit diagram for the embodiment
according to FIG. 2;
FIG. 5 shows the vector diagram belonging to the circuit diagram of
FIG. 3;
FIG. 6 shows a block diagram of the position control of the primary
element .
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows an apparatus according to the invention in which the
primary element 1 of an inductive transmitter is brought into an
approach position with respect to the secondary element 2 of the
transmitter, which is located on the underside of an electric car
3. As will be explained in detail in connection with FIG. 6, the
primary element 1 is moved by a sensor-controlled mechanism,
corresponding to the different phases of the charging process. In
the embodiment according to FIG. 1, the secondary element 2 is
disposed to be readily accessible on the underside of the electric
car 3. On the other hand, the option exists of disposing it at
other locations on the vehicle 3, and covering it for mechanical
protection against environmental influences, such as dirt, etc.
This option makes the secondary element 2 readily accessible as
soon as the vehicle 3 is brought into the approach position with
respect to the primary element 1 of the transmitter. As soon as the
secondary element 2 is readily accessible, the primary element 1
can be brought into a predetermined position with respect to the
secondary element 2 by means of a sensor-controlled motor. The
invention is based on the realization that, if transmitting
elements 1, 2 and the primary- and secondary-side electronic
components are correspondingly designed, at a medium frequency of,
for example, 25 kHz, electrical energy can be transmitted from
primary element 1 to secondary element 2 via an air gap of a
magnitude of up to approximately 1 cm. A slotted guide for the
primary element 1 is therefore not necessary. With respect to
energy and signals, the primary element 1 is connected to the
charging device 6 via lines 5. The generation of the medium
frequency of, for example, 25 kHz, and the setting of the output,
take place in the charging device 6. In the example of FIG. 1, the
transmission system is connected to a three-phase network of 400
volts and 50 Hertz. This type of solution is advantageous for fast
charging with charge outputs in the 10 kW range, for example in
parking garages while the owner shops. A home charging device of
low output can be placed on the vehicle 3, beneath the secondary
element 2, with a primary element that can be adjusted in height.
The secondary element 2 is connected to a rectifier 7, by way of
which the battery of the electric car 3 is charged.
Primary element 1 and secondary element 2 of the inductive
transmitter are essentially inductive coils which are designed for
an energy transmission via an air gap, have a soft-magnetic core
and are cast integrally in plastic or the like to provide
insulation against the environment. FIG. 2 shows a simple
embodiment of such an indicative transmitter. Primary element 1 and
secondary element 2 are configured in shell shape, and face one
another with spacing .delta.. Ferrites are suitable magnetic
materials. This transmitter is distinguished from a conventional
transformer by the influence of the air gap .delta. on the magnetic
flux density B and the magnetization current I.mu.. The
relationship between the two values is illustrated by the
characteristic curve of the magnetization of the soft-magnetic
material. The magnetization current I.mu. is typically small with
respect to the current I.mu. transmitted to the input circuit. In a
contactless transmitter, as in FIG. 2, the magnetization current
I.mu. is proportional to the product of the magnetic flux density B
and the gap width .delta.. Because the magnetization current does
not contribute to the output transport, but, like the transmitted
current, causes losses and stresses the source, it is necessary to
limit it as of a limit gap width .delta..sub.g to the intensity of
the transmitted current I'. Therefore, above the limit gap width,
the magnetic flux density B must be lowered reciprocally to the gap
width. With larger gap widths, it is significantly lower than the
values typically in magnetic materials. Nevertheless, when the
transmitters are of small dimensions, the frequency f must be
sufficiently high for a large voltage U and a corresponding output
to be transmitted. In transmitters that are not thermally charged
to capacity, the transmittable output P is proportional to the
frequency f. With a given gap width .delta., however, it is not
possible to arbitrarily reduce the field cross-section A and the
diameter D of a transmitter by increasing the frequency. As the
diameter D decreases, the portion of the magnetic flux leakage that
only surrounds one winding increases, at the cost of the main flux
linked to the two windings. This causes the magnetic coupling of
the windings and the transmitted voltage to decrease and the
inductive resistance in the circuits to increase. With gap widths
in the cm range, transmission elements having a diameter of 20 to
25 cm are required for outputs of 1 kW to 10 kW. The winding height
h is small in relation to the diameter D. The transmitter elements
therefore have a flat structural shape. With large gap widths, they
comprise ferrite plates with flat coils placed on top of them. To
avoid the high eddy-current losses which occur at high frequencies,
the coil conductors are constructed from thin, insulated individual
wires having a layer that varies inside the cross-section.
Contactless transmission elements for 25 kHz require only a small
percentage of the material needed for 50-Hertz transformers of
identical output, so that their output-related losses are also
smaller.
FIG. 3 shows a possible embodiment of a medium-frequency source
connected to the primary element 1 and of the rectifier 7 connected
to the secondary element 2. In this instance, UB1 and UB2
respectively indicate the operating voltage of the inverter and the
voltage of the battery to be charged. IL indicates the charging
current transmitted by way of the elements 1 and 2. Contactless
transmission of information takes place between the charging
current setter 310 of a inverter 7 and the charging current
controller 300 of the battery. The charging current controller 300
obtains its desired value for charging current control from battery
status detection. This detection uses sensors for detecting the
battery voltage UB2, the discharge current IE, the charging current
IL, the temperature .theta. and possibly further values that
characterize the status of the battery, as well as a processor and
a memory, with whose assistance the status of the battery can be
tracked over its service life. The desired charging current value
is selected to correspond to the determined battery status, and the
deviation .DELTA.J is transmitted to the actual charging current
setter 310 of the inverter.
FIG. 4 shows an equivalent circuit diagram of the circuit according
to FIG. 2. Accordingly, the primary leakage inductance L.sigma.1 of
the transmitter, with the parallel circuit of the two capacitors
C1/2 of the inverter, forms a series resonant circuit. In contrast,
the secondary side of the transmitter and the capacitor C2 form a
parallel resonant circuit. The electrical values shown relate to
the fundamental modes. The input voltage U1 is the fundamental mode
of the inverter voltage UW. The mode amplitudes can be set by means
of changing the inverter frequency or modulating the percentage
duty cycle of the power semiconductors T1, T2. The further
observations are based on the second method, which permits the
setting of the voltage fundamental modes U1 at a nearly constant
frequency. The highest input voltage U1 and the greatest mode
amplitudes result in T1 and T2 turn-on times of identical length.
The steady state is characterized by the turn-on ratio of the power
semiconductors T1 and in which the desired charging current IL
flows and the primary-side voltage source UB1 delivers just the sum
of secondary-side charging output and switching losses. The
function of the transmission method is described more precisely in
the vector diagram in FIG. 5. As the capacitor voltage U2 passes
through zero, the nearly constant battery current IB2 is commutated
from one bridge diagonal to the other. On the side of the
alternating current, the fundamental mode IL of this current is
identical in phase to the capacitor voltage U2. The capacity of the
capacitor C2 is selected such that, at maximum charging current,
the secondary-side leakage voltage U.sigma.2 is completely
compensated, i.e., in this operating state, the transmitting
secondary side, with the rectifier load and the capacitor C2, acts
virtually like a resistor connected in parallel with the primary
inductance M. In the vector diagram, this is shown by the small
phase angle .phi.2 between the primary field voltage U.sub.h and
the secondary current I2. The primary-side leakage inductance
L.sigma.1 and the counter-inductance M are compensated by the two
capacitors C1/2 of the inverter to the extent that only a small
phase shift .phi.1 exists between the input voltage U1 and the
input current I1 on the primary side. The leakage factor of
.sigma.=0.45 used in the vector diagram corresponds to a mechanical
air gap of approximately 1.5 cm in a pot-core transmitter according
to FIG. 2.
The switching elements are designed such that the series resonant
circuit of the primary side and the parallel resonant circuit of
the secondary side resonate at the same frequency. The maximum
output is transmitted at the resonance point.
The battery-charging current IL is measured inductively in FIG. 3.
The measuring current IM is supplied to the charging current
controller 300. As explained above, the current deviation .DELTA.I
transmitted to the charging current setter 310 changes either the
inverter frequency or the percentage duty cycle of the power
semiconductors T1 and T2 until the required charging current has
been set.
FIG. 6 shows the block diagram of an arrangement for automated
charging. The arrangement comprises the middle-frequency current
source and coupling apparatus MFK of the charging device and the
rectification, detection and control apparatus GER on the vehicle
3. After the charging device has been activated, for example by the
deposit of a coin, a switch-on pulse EI is emitted by the vehicle
3, for example by way of a key. This switch-on pulse produces the
orientation signal OS via the input S of the orientation signal
connector OSG. At the same time, the start signal generator STG is
reset via the resetting input R, and the signal FSB, "vehicle ready
for start," is cut off. The orientation signal OS is only applied
to the input of the frequency modulator FMD. It modulates a
high-frequency generator HFG. The high-frequency signal HF reaches
the transmission element UEF 2 on the bottom of the vehicle via a
frequency-dividing network FWF. A coupling to the transmission
element of the charging element 1 arises by way of the
electromagnetic field emitted by the transmission element 2. The
high-frequency signal HF received by the charging transmission
element 1 is separated from the power circuit of the coil by the
frequency-dividing network FWL, and supplied to a frequency
modulator FDM and a peak rectifier SG. The peak rectifier SG
rectifies the amplitudes of the high-frequency signal and supplies
them to an analog/digital converter AD. The output signal NA
continuously indicates the digital value of the newest amplitude.
This amplitude value is now supplied to a memory SAA in the rhythm
of a clock signal produced by the clock generator TG. With each
clock signal, the old amplitude signal that was stored during the
previous cycle appears at the output of the memory SAA. The
respectively newest amplitude signal NA and the old amplitude
signal AA are supplied to a comparison stage VS. The comparison of
the old amplitude signal AA and the newest amplitude signal NA
indicates whether a signal increases, remains the same or becomes
smaller. As the amplitude increases, the newest amplitude signal is
constantly greater than the old one. This is shown by the
comparison stage, with a logical-level 1 at its output VS1. If the
amplitude no longer changes, the old and new amplitude signals are
identical. This is shown by the output VS2, with a logical 1. If,
in contrast, the old amplitude signal AA is greater than the new
amplitude signal, that is, the amplitude decreases, the signal VS3
is logical-level 1. These amplitude comparison signals are supplied
to a drive guide and coupling device AFK. The drive guide and
coupling device AFK controls the drives A.PHI., Az and Ar of the
coupling mechanism. The drive A.phi. moves a rotary disk, on which
the drive Az for adjusting the height of the charging transmission
element 1 is mounted. The drive Az moves the drive Ar in the
vertical direction by way of a spindle. The drive Ar extends an
arm, which supports the transmission element 1, in the radial
direction. All three drives form a kinematic chain, i.e., the
movements of the individual coordinates add in space. The control
of the 3 drives is effected by means of the amplitude comparison
signals VS1, VS2, VS3 in such a way that the charging transmission
element 1 is always guided in the direction of increasing
amplitudes of the received HF signal. With the occurrence of the
orientation signal OS, the drive guide and coupling device AFK
triggers, for example, a rotational movement of the arm to the
left. If the amplitude increases, the movement is continued until
the maximum has been reached. If, in contrast, the amplitude
decreases, the direction of rotation is reversed. If the best
possible proximal position of the two transmission elements is
reached due to the rotational movement, that is, the amplitude no
longer changes, which is indicated by the signal VS2, the
rotational movement is halted and the drive Ar for extending the
arm in the radial direction is actuated. The charging transmission
element 1 now moves in the radial direction toward the transmission
element 2 on the vehicle 3 until the charging transmission element
1 comes to stand directly beneath the transmission element 2 on the
vehicle 3. The maximum HF signal is to be anticipated in this
position. Finally, the vertical movement is effected via the drive
Az until the two transmission elements touch one another. To
increase the coupling precision, the approach attempt can be
repeated. To this end, the charging transmission element 1 is moved
back in the z-direction by a few millimeters, so that there is no
more contact between the two transmission elements. When the
approach process is re-initiated, it is to be expected that higher
coupling precision will be achieved when the approach is made from
a lesser initial distance. When the two transmission elements
subsequently touch, the drives are halted and the signal "coupling
achieved," KER, is emitted by the drive guide and coupling device
AFK. The signal "coupling achieved" KER is supplied to a keyed or
on/off signal generator TSG. The keyed signal generator TSG
converts the signals to be sent to the vehicle 3 into a keyed
modulation of the inverter output current. For this purpose, the
keyed signal TSI switches the inverter on and off in a rhythm
typical for signals. During this signal emission, the current
reference value converter SFU of the inverter is still located in
the base position, in which only one current reference value Is
used for transmitting the keyed signals is connected to the current
reference value input IFE of the inverter. In the charging
transmission element 1, the middle frequency output current MFI of
the inverter, which is modulated in the rhythm of the signal KER,
now generates an electromagnetic field that is modulated to
correspond to the keyed signal and induces a corresponding voltage
in the charging transmission element 2. The information obtained in
the rhythm of the keying is now demodulated by the keyed signal
demodulator TSD. The signal "coupling achieved" KER received on the
vehicle switches off the orientation signal connector OSG via the
reset input R, and switches on the charging initiation signal
generator LAG via the setting input S. At the same time, a timing
stage .DELTA.TL, which limits the duration of the charging
initiation signal LA, is activated. After the time .DELTA.TL has
expired, the switch is automatically made from the charging
initiation signal LA to the current deviation signal .DELTA.I in
the clock generator TG. The charging initiation signal LA
transmitted to the charging apparatus on the same path as the
orientation signal OS now switches on the charging operation memory
LBS and thus switches on the inverter. Moreover, the current
reference value converter SFU is switched from the current
reference value IS to the current reference signal .DELTA.I
subsequently emitted by the frequency modulator FDM. The current
reference value signal .DELTA.I is a measure for the necessary
increase in the battery charging current. This signal is formed by
the charging current controller LSR on the vehicle, and corresponds
to the difference between the desired value LIS of the charging
current and the actual charging current detected by the measuring
signal IM. The measuring signal IM is obtained from the transmitted
current MFI by means of the measurement converter MW. The desired
value LIS of the charging current is formed by the detection BZE of
the battery state. The detection of the battery state monitors the
charging current, the discharge current, the temperature and other
values of the battery that are relevant to the state of the
battery, and thus knows the charging current need in each charging
state. The desired value LIS for the charging current is switched
from the battery state detection to the charging current controller
with the setting of the current deviation indicator .DELTA.IG by
the charging current switching signal LLS. If the battery is
charged, the battery state detection switches on the charging end
signal generator LEG via the signal BGL. For this purpose, the
signal BGL is supplied via the OR stage V1 to the setting input of
the charging end signal generator LEG, together with a switch-off
signal which can be predetermined manually by a keyed generator and
breaks off the charging process. At the same time the charging end
signal generator LEG is set, the current deviation signal generator
.DELTA.IG is reset in its base position. Instead of the current
deviation signal, the charging end signal is now transmitted to the
charging device. The charging end signal resets the charging
operation memory LBS in its base position. Thus, the inverter and
current transmission to the vehicle are shut off. At the same time,
in the drive guide and coupling device AFK, the charging end signal
triggers the recall of the drive coordinates in the base position.
Once they have reached the base position, the end switch ESr is
operated by the radius coordinates, and the end switch ESZ is
operated by the SZ-coordinates, The drive guide and coupling device
AFK subsequently emits the start release signal SFR. The start
release signal now switches the inverter on and off again via the
keyed signal generator TSG and the keyed signal TSI. In this
decoupled state of the transmission elements 1 and 2, no energy can
be transmitted, but a sufficiently high signal voltage is induced
in the transmission element 2 to demodulate the keyed signal
demodulator on the vehicle. The demodulated start release signal
SFR now resets the charging end signal generator LEG and brings the
start signal generator STG into the "vehicle ready to start"
position, which is indicated by the signal FSB.
It will be understood that the above description of the present
invention is susceptible to various modifications, changes and
adaptations, and the same are intended to be comprehended within
the meaning and range of equivalents of the appended claims.
* * * * *